ext4: Use ext4_journal_extend() instead of jbd2_journal_extend()

Use ext4 helper ext4_journal_extend() instead of opencoding it in
ext4_try_to_expand_extra_isize().

Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20191105164437.32602-8-jack@suse.cz


Signed-off-by: Theodore Ts'o <tytso@mit.edu>